The present invention generally relates to a method for repairing an in-ground tunnel structure. More particularly, the method involves forming water drainage holes in the tunnel structure and sealing the holes with a curable resin such as an epoxy. The method further involves applying a curable resin to the inside wall surfaces of the tunnel to form a hardened resinous liner. The resulting composite tunnel structure has high mechanical strength and is resistant to water leaks.
There are numerous tunnel structures that run underground throughout the world. Railroad tracks, subway tracks, communication cables, electrical lines, and other equipment are laid in such tunnels. In many instances, the tunnels are built in rocky areas. Dynamite and other explosives are used to blast the rock-lined subterranean layers and clear an underground area for building the tunnel. The tunnel structure may be made from a wide variety of materials including rocks, steel, sheet metal, concrete blocks, and bricks. The tunnel structure includes archways, interior walls, and ground platform sections. If concrete blocks or bricks are used to fabricate the tunnel structure, these materials typically are held together by cement, mortar, or other bonding agents. In addition, the interior walls of the tunnel typically are lined with a cementitious liner. The cementitious liner can be produced by applying a cement mixture over the interior walls and smoothing-out the mixture to form a uniform cementitious layer. The cementitious layer provides a smooth and hard lining for the interior surface of the tunnel. Moreover, the cementitious liner helps to seal the interior walls and prevent fluids from leaking into the passageway of the tunnel.
However, over a period of time, the tunnel tends to deteriorate due to ordinary aging, corrosive action of fluids being transported in the tunnel, unusual environmental conditions, and other reasons. Cracks, holes, and other defects may develop in the walls of the tunnel. If the wall structure of the tunnel decays substantially, then ground water may seep or flow freely through the tunnel walls. The penetration of the ground water into the tunnel passageway may cause hazardous conditions.
For example, in cold climates, the seeping water may freeze and form icebergs, icicles, and other icy buildup. If the icy buildup comes into contact with a high voltage line (for example, a line having 13,200 volts), the line can ground out. This can lead to fire, explosions, and other hazardous conditions. Any electrical lines or communication cables that are running through the tunnel can be damaged or destroyed.
There are various known methods for rehabilitating existing underground tunnel structures. For example, Pulkkinen, U.S. Pat. No. 4,695,188 discloses a method for treating a rock cistern or tunnel that may be used to store pressurized gases and liquids. The method involves coating an inner lay with a tightly sealing material such as plastic, steel, or concrete fibers. An intermediate layer comprising a steel-reinforced, water-tight, concrete composition is sprayed over the inner layer. An outer layer comprising a concrete mixture of haydite, sand, cement, swelling agents, and water-conducting fibers is sprayed over the intermediate layer. The outer layer is water-permeable and used for conducting the ground water.
Fernando, U.S. Pat. No. 4,915,542 discloses a method of waterproofing the inner surfaces of tunnels, channels and mine galleries. In the method described in the '542 patent, sheets of material are unrolled and cut in situ and applied to the inner wall surfaces. Holes are cut into the walls through the sheets and anchors are attached to the walls. The sheets are waterproof and fireproof, provide good thermal insulation properties, have tear-resistance and moisture-resistance features, and are heat-sealable.
Weholt, U.S. Pat. No. 4,940,360 discloses an insulating and rehabilitation system for the prevention of ice buildup on tunnel arches, walls, and base sections. The tunnel liner system comprises a combination of prefabricated modular wall panels and arch panels that conform with the dimensions and clearance requirements of the tunnel. The liner panels are joined together by cam-lock fasteners. A lightweight, chemically-hardening structural fill composition can be injected in the voids located between the rock face of the tunnel and liner panels. The structural fill composition can include a mixture of polystyrene beads, wetting agents, organic fibers, Portland cement, and sand.
James, U.S. Pat. No. 6,402,427 discloses a method for reinforcing the brick lining of a tunnel. The method involves cutting T-shaped grooves into the brick lining. One or more reinforcement rods, which are encased in a fabric sleeve, are inserted through the narrow mouth of each groove (the stem region of the “T”) so that they rest within the enlarged part of the groove (the cross-bar region of the “T”). Grout is injected into the fabric sleeve so that it expands against the groove, and some grout seeps through the sleeve to bond to the brick lining. Anchoring holes may be drilled through the brick lining and into the surrounding rock. Expansion bolts are inserted into the anchoring holes and secured to the ends of the reinforcement rods.
Although the above-described conventional methods of lining tunnel structures with fabricated sheets and panels can be effective somewhat in rehabilitating such structures, these repair methods can be cumbersome and time-consuming. For instance, the modular sheets and panels must be fitted carefully inside of the tunnel so that they conform tightly to the archways and wall sections. After this fitting step has been completed, the sheets and panels must be fastened in place by anchors, bolts, and the like. Furthermore, the modular liner sheets and panels and other materials used in these conventional repair systems can be costly.
There is a need for an improved method for repairing in-ground tunnel structures that does not involve installing sheets, panels, and other mechanical supports in the tunnel. The method should be relatively quick and practical so that it can be used on a wide variety of tunnel structures. The method should also be economically feasible. The present invention provides such an improved method for repairing in-ground tunnels. The improved method involves applying a first curable resin to the interior wall surfaces of the tunnel, drilling drainage holes in the wall structure of the tunnel, and filling the drainage holes with a second curable resin. The resins are allowed to cure and harden, thereby sealing the wall surfaces and drainage holes. The resulting composite tunnel structure has high mechanical integrity and is resistant to water leaks. These and other objects, features, and advantages of this invention are evident from the following description and attached figures.